Magnetoresistive effect element and magnetic memory device

ABSTRACT

A magnetoresistive effect element may be given satisfactory magnetic characteristics because a deterioration of a magnetoresistive changing rate by annealing can be suppressed and a magnetic memory device includes this magnetoresistive effect element to provide excellent write characteristics.  
     A magnetoresistive effect element has a pair of ferromagnetic layers (magnetization fixed layer  5  and magnetization free layer  7 ) opposed to each other through an intermediate layer  6  to cause an electric current to flow in the direction perpendicular to the layer surface to obtain a magnetoresistive change. A magnetic memory device comprises the magnetoresistive effect element 1 in which at least one of the pair of ferromagnetic layers  5, 7  contains an amorphous ferromagnetic material whose crystallization temperature is higher than 623 k and bit lines and word lines sandwiching this magnetoresistive effect element and the magnetoresistive effect element in the thickness direction.

TECHNICAL FIELD

[0001] The present invention relates to a magnetoresistive effectelement having an arrangement to obtain a magnetoresistive change bycausing an electric current to flow in the direction perpendicular tothe layer surface and a magnetic memory device including themagnetoresistive effect element.

BACKGROUND ART

[0002] Information communication devices, in particular, personal smalldevices such as personal digital assistants are making great spread,elements such as memories and logics comprising informationcommunication devices are requested to have higher performance such ashigher integration degree, higher operation speed and lower powerconsumption. In particular, technologies for making nonvolatile memoriesbecome higher in density and larger in storage capacity areprogressively increasing their importance as technologies forreplacements of hard disk and optical disc that cannot be essentiallyminiaturized because they have movable portions.

[0003] As nonvolatile memories, there may be enumerated flash memoriesusing semiconductors and an FRAM (Ferro electric Random Access Memory)using ferroelectric material and the like.

[0004] However, the flash memory encounters with a drawback that itswrite speed is as slow as the microsecond order. On the other hand, ithas been pointed out that the FRAM has a problem in which it cannot berewritten so many times.

[0005] A magnetic memory device called an MRAM (Magnetic Random AccessMemory) described in “Wang et al., IEEE Trans. Magn. 33 (1977), 4498”,receives a remarkable attention as a nonvolatile memory which canovercome these drawbacks. Since this MRAM is simple in structure, it caneasily be integrated at a higher integration degree. Moreover, since itis able to record information based upon the rotation of magneticmoment, it can be rewritten so many times. It is also expected that theaccess time of this magnetic random access memory will be very high, andit was already confirmed that it can be operated at the access time ofnanosecond order.

[0006] A magnetoresistive effect element for use with this MRAM, inparticular, a tunnel magnetoresisitve effect (Tunnel Magnetoresistance:TMR) element is fundamentally composed of a lamination layer structureof a ferromagnetic tunnel junction of ferromagnetic layer/tunnel barrierlayer/ferromagnetic layer. This element generates magnetoresistiveeffect in response to a relative angle between the magnetizationdirections of the two magnetic layers when an external magnetic field isapplied to the ferromagnetic layers under the condition in which aconstant current is flowing through the ferromagnetic layers. When themagnetization directions of the two magnetic layers are anti-parallel toeach other, a resistance value is maximized. When they are parallel toeach other, a resistance value is minimized. Functions of memory elementcan be demonstrated by creating the anti-parallel state and the parallelstate with application of the external magnetic field when themagnetization direction of one ferromagnetic layer is inverted.

[0007] In particular, in a spin-valve type TMR element, when oneferromagnetic layer is antiferromagnetically coupled to the adjacentantiferromagnetic layer, it is set to the magnetization fixed layer ofwhich magnetization direction is constantly made constant. The otherferromagnetic layer is set to the magnetization free layer of whichmagnetization direction is easily inverted with application of anexternal magnetic field and the like. Then, this magnetization freelayer becomes an information recording layer in a magnetic memory.

[0008] In the spin-valve type TMR element, its resistance changing ratiois expressed by the following equation (A) where P1, P2 represent spinpolarizabilities of the respective ferromagnetic layers.

2P1P2/(1-P1P2)  (A)

[0009] As described above, the resistance changing ratio increases asthe respective spin polarizabilities increase. With respect to arelationship between materials for use with ferromagnetic layers andthis resistance changing ratio, ferromagnetic chemical elements of Fegroup such as Fe, Co, Ni and alloys of three kinds thereof have alreadybeen reported so far.

[0010] Information is read out from the TMR element of the MRAM basedupon a difference current with application of a constant bias voltage ora difference voltage with application of a constant bias current in thestate of “1”, for example, obtained when directions of magnetic momentsof one ferromagnetic layer and the other ferromagnetic layer sandwichingthe tunnel barrier layer are anti-parallel to each other and aresistance value is high and in the state of “0” obtained when thedirections of the magnetic moments are parallel to each other.

[0011] Accordingly, a higher TMR ratio (magnetoresistive changing ratio)is advantageous, and hence a high-speed memory having a high integrationdegree and a low error rate can be realized.

[0012] In addition, the TMR element having the ferromagneticlayer/tunnel barrier layer/ferromagnetic layer has a bias voltagedependence of TMR ratio, and it is known that the TMR ratio decreases asthe bias voltage increases. Since it is known that, in most cases, aread signal takes a maximum value at a voltage (Vh) in which a TMR ratiodecreases to the half depending on the bias voltage dependence wheninformation is read out the magnetic memory by a difference current or adifference voltage, a small bias voltage dependence is effective fordecreasing read errors.

[0013] The MRAM includes switching elements such as transistors toselect a TMR element, in addition to the above-mentioned TMR element,and has a semiconductor circuit including the switching element.

[0014] When such semiconductor circuit and the TMR element coexistwithin the same chip, since a semiconductor circuit manufacturingprocess requires a process for heating the chip at temperature in excessof 350° C., the TMR element needs similar temperature durability.

[0015] However, it is known that a TMR element having a ferromagneticlayer made of alloy of Fe-group chemical element such as Fe, Co and Niis considerably deteriorated in magnetoresistive changing ratio attemperature higher than about 300° C., and therefore it has a problemfrom a heat-resisting property standpoint. This magnetoresistivechanging ratio may be deteriorated by undesired impurities entered intothe ferromagnetic layer or the tunnel barrier layer after components oflayers comprising the TMR element have been mutually diffused by heat.

[0016] Therefore, when the magnetization free layer is made of amorphousalloy in which B, Si, C, P, Al, Ge, Ti, Nb, Ta, Zr, Mo are added to thealloy of the Fe-group chemical element such as Fe, Co and Ni, themagnetoresistive changing ratio can be improved and the magnetizationdirection can be inverted with stability so that read characteristics inthe MRAM can be improved.

[0017] However, when such amorphous alloy is heated at temperaturehigher than its crystallization temperature, magnetic characteristics,those requested for the TMR element for use with MRAM, such asmagnetoresistive changing ratio are deteriorated.

[0018] As described above, in order to realize the MRAM that can makethe excellent read characteristics and high affinity of thesemiconductor circuit manufacturing process become compatible with eachother, the magnetic characteristics (high magnetoresistive changingratio, etc.) of the TMR element should be guaranteed after the magneticelement has experienced relatively high temperature. For this reason, ithas been requested so far to improve heat-resisting property of the TMRelement.

[0019] In order to solve the above-mentioned problems, it is an objectof the present invention to provide a magnetoresistive effect elementhaving satisfactory magnetic characteristics in which deterioration of amagnetoresistive changing ratio due to annealing can be suppressed and amagnetic memory device including this magnetoresistive effect elementand which has excellent write characteristics.

DISCLOSURE OF THE INVENTION

[0020] A magnetoresistive effect element according to the presentinvention has a pair of ferromagnetic layers opposed to each otherthrough an intermediate layer to obtain a magnetoresistive change bycausing an electric current to flow in the direction perpendicular tothe layer surface, at least one of the ferromagnetic layers containingan amorphous ferromagnetic material of which crystallization temperatureis higher than 623 K.

[0021] A magnetic memory device according to the present inventioncomprises a magnetoresistive effect element having a pair offerromagnetic layers opposed to each other through an intermediate layerto obtain a magnetoresistive change by causing an electric current toflow in the direction perpendicular to the layer surface and a word lineand a bit line sandwiching this magnetoresistive effect element in thethickness direction, one of the pair of ferromagnetic layers containingan amorphous ferromagnetic material of which crystallization temperatureis higher than 623 K.

[0022] According to the above-mentioned arrangement of themagnetoresistive effect element of the present invention, since at leastone of the pair of ferromagnetic layers contains the amorphousferromagnetic material of which crystallization temperature is higherthan 623 K, heat-resisting temperature can be improved, and henceheat-resisting property of the magnetoresistive effect element can beimproved.

[0023] According to the above-mentioned arrangement of the magneticmemory device of the present invention, since the magnetic memory deviceincludes the magnetoresistive effect element and the word line and thebit line sandwiching the magnetoresistive effect element in thethickness direction and the magnetoresistive effect element is themagnetoresistive effect element of the present invention, heat-resistingproperty can be improved, and hence a magnetoresistive changing ratiocan be suppressed from being lowered due to annealing and excellent readcharacteristics can be realized.

BRIEF DESCRIPTION OF DRAWINGS

[0024]FIG. 1 is a schematic diagram showing a TMR element according toan embodiment of the present invention;

[0025]FIG. 2 is a schematic diagram showing a TMR element having alamination layer ferri-strucutre;

[0026]FIG. 3 is a schematic cross-sectional view showing a main portionof a cross-point type MRAM including the TMR element according to thepresent invention as a memory cell;

[0027]FIG. 4 is a cross-sectional view showing the memory cell shown inFIG. 3 in an enlarged-scale;

[0028]FIG. 5 is a plan view of a TEG for use in estimating a TMRelement;

[0029]FIG. 6 is a cross-sectional view taken along the line A-A in FIG.5;

[0030]FIG. 7 is a diagram showing a relationship among Si content, Bcontent and crystallization temperature;

[0031]FIG. 8 is a diagram showing a relationship among Si content, Bcontent and a TMR ratio;

[0032]FIG. 9 is a diagram showing a relationship among Si content, Bcontent and a TMR ratio (obtained after annealing at 350° C.);

[0033]FIG. 10 is a diagram showing a relationship betweencrystallization temperature and a deterioration rate of a TMR ratio; and

[0034]FIG. 11 is a diagram showing optimum composition range of Sicontent and B content.

BEST MODE FOR CARRYING OUT THE INVENTION

[0035] The present invention relates to a magnetoresistive effectelement having a pair of ferromagnetic layers opposed to each otherthrough an intermediate layer to obtain a magnetoresistive change bycausing an electric current to flow in the direction perpendicular tothe layer surface, the magnetoresistive effect element having the pairof ferromagnetic layers in which at least one of them contains anamorphous ferromagnetic material of which crystallization temperature ishigher than 263 K.

[0036] According to the present invention, the above-describedmagnetoresistive effect element is a spin-valve type magnetoresistiveeffect element in which one of the pair of ferromagnetic layers is amagnetization fixed layer and the other is magnetization free layer.

[0037] According to the present invention, the magnetoresistive effectelement is a tunnel magnetoresistive effect element using a tunnelbarrier layer made of an insulating material or a semiconductor as anintermediate layer.

[0038] According to the present invention, the above-describedmagnetoresistive effect element has a synthetic ferrimagnet structure.

[0039] According to the present invention, in the above-describedmagnetoresistive effect element, the amorphous ferromagnetic material isa ferromagnetic material mainly composed of any one of or more than twokinds of Fe, Co, Ni and which contains more than any one kind of B, Si,C, P, Al, Ge, Ti, Nb, Ta, Zr, Mo as added elements.

[0040] According to the present invention, there is provided a magneticmemory device comprising a magnetoresistive effect element having a pairof ferromagnetic layers opposed to each other through an intermediatelayer to obtain a magnetoresistive change by causing an electric currentto flow in the direction perpendicular to the layer surface and wordlines and bit lines sandwiching the magnetoresistive effect elements inthe thickness direction, at least one of the pair of ferromagneticlayers containing an amorphous ferromagnetic material of whichcrystallization temperature is higher than 263 K.

[0041] Also, according to the present invention, in the above-describedmagnetic memory device, the magnetoresistive effect element is aspin-valve type magnetoresistive effect element in which one of the pairof ferromagnetic layers is a magnetization fixed layer, the other beinga magnetization free layer.

[0042] Also, according to the present invention, in the magnetic memorydevice, the magnetoresistive effect element is a tunnel magnetoresistiveeffect element using a tunnel barrier layer made of an insulatingmaterial or a semiconductor as the intermediate layer.

[0043] Also, according to the present invention, in the above-describedmagnetic memory device, the magnetoresistive effect element has asynthetic ferrimagnet structure.

[0044] Additionally, according to the present invention, the amorphousferromagnetic material is a ferromagnetic material mainly composed ofany one of or more than two kinds of Fe, Co, Ni and which contains morethan any one kind of B, Si, C, P, Al, Ge, Ti, Nb, Ta, Zr, Mo as addedelements for making a ferromagnetic layer become an amorphousferromagnetic layer.

[0045]FIG. 1 is a schematic diagram showing an arrangement of amagnetoresistive effect element according to an embodiment of thepresent invention. The embodiment shown in FIG. 1 shows the case inwhich the present invention is applied to a tunnel magnetoresistiveeffect element (hereinafter referred to as a “TMR element” ).

[0046] This TMR element 1 has a substrate 2 made of a suitable materialsuch as silicon on which there are laminated an underlayer 3, anantiferromagnetic layer 4, a magnetization free layer 5, which is aferromagnetic layer, a tunnel barrier layer 6, a magnetization freelayer 7, which is a ferromagnetic layer and a top-coat layer 8, in thatorder.

[0047] More specifically, this tunnel magnetoresistive effect elementconstructs a so-called spin-valve type TMR element in which one of theferromagnetic layers is the magnetization fixed layer 5, the other beingthe magnetization free layer 7. The magnetization fixed layer 5 and themagnetization free layer 7 that are the pair of ferromagnetic layerssandwich the tunnel barrier layer 6 to form a ferromagnetic tunneljunction 9.

[0048] When this TMR element 1 is applied to a suitable magnetic devicesuch as a magnetic memory device, the magnetization free layer 7 becomesan information recording layer to record therein information.

[0049] The antiferromagnetic layer 4 is coupled antiferromagnetically tothe magnetization fixed layer 5, which is one of the ferromagneticlayers, to prevent the magnetization direction of the magnetizationfixed layer 5 from being inverted with application of an electriccurrent field used to write information so that the magnetizationdirection of the magnetization fixed layer 5 can constantly be madeconstant. More specifically, in the TMR element 1 shown in FIG. 1, themagnetization direction of the magnetization free layer 7, which is theother ferromagnetic layer, is inverted by a suitable means such as anexternal magnetic field. The magnetization free layer 7 becomes a layerto record therein information when it is applied to a suitable meanssuch as a magnetic memory device, and is therefore referred to as an“information recording layer”.

[0050] As materials comprising the antiferromagnetic layer 4, there canbe used Mn alloy containing Fe, Ni, Pt, Ir, Rh and the like, Co oxide,Ni oxide and so on.

[0051] In the spin-valve type TMR element 1 shown in FIG. 1, themagnetization direction of the magnetization fixed layer 5 is madeconstant when it is coupled to the antiferromagnetic layer 4antiferromagnetically. Therefore, the magnetization direction of themagnetization fixed layer 5 is not inverted with application of anelectric current field used to write information.

[0052] The tunnel barrier layer 6 is the layer used to magneticallyseparate the magnetization fixed layer 5 and the magnetization freelayer 7 from each other and which is used to allow a tunnel electriccurrent to flow therethrough.

[0053] Oxides such as Al, Mg, Si, Li, Ca, nitride and halogenide can beused as materials comprising the tunnel barrier layer 6.

[0054] The tunnel barrier layer 6 can be obtained oxidizing or nitridinga metal film that has been deposited by a suitable method such as asputtering method or a vapor-evaporation method.

[0055] Additionally, this tunnel barrier layer can be obtained by a CVDmethod using organic metals, oxygen, ozone, nitrogen, halogen,halogenide gas and so on.

[0056] In accordance with this embodiment, at least one of themagnetization fixed layer 5 and the magnetization free layer 7, whichare the pair of ferromagnetic layers comprising, in particular, theferromagnetic funnel junction 9, contains an amorphous ferromagneticmaterial of which crystallization temperature is higher than 623 K.

[0057] Conventional TMR elements having ferromagnetic layers(ferromagnetic layers in this case are amorphous ferromagnetic layers)composed of only ferromagnetic transition metal elements or TMR elementsusing as ferromagnetic layers amorphous ferromagnetic layers withcrystallization temperature lower than 623 K encounter with defects inwhich a TMR ratio is deteriorated by annealing required in asemiconductor circuit manufacturing process and the like or a rectangleratio of an R—H loop (resistance-magnetic field curve) is deteriorated.

[0058] On the other hand, the above-mentioned defects can be improved bythe ferromagnetic layer made of an amorphous ferromagnetic materialwhose crystallization temperature is higher than 623 k.

[0059] Although a cause for achieving such effect is not clear, since acomparison of the crystal ferromagnetic layer and the amorphousferromagnetic layer reveals that a metalloid element such as B and Siadded to make the crystal ferromagnetic layer become an amorphousferromagnetic layer has a covalent bonding with Fe-group ferromagneticelements such as Co, Fe, Ni which are main components microscopicallyand a structure of a short period range has a quality close to that ofan intermetallic compound such as Co₃B, Co₂B, Co₂Si, bond energy is highand bond between the ferromagnetic metal element and the metalloidelement is relatively strong, and hence these undesired elements can besuppressed from being diffused into the tunnel barrier layer.

[0060] Also, in the amorphous magnetic material having crystallizationtemperature higher than 623 K, its amorphous structure may be stable athigher temperature, and a disordered structure peculiar to the amorphousstructure may be maintained at high temperature in the long periodrange. In addition, since the amorphous magnetic material has bondhaving a covalent bond-like element in the short period range, theseundesired elements can be suppressed from being diffused into the tunnelbarrier layer 6 at higher temperature.

[0061] As compared with the magnetic element in which the magnetizationfree layer is made of the crystal ferromagnetic material, the magneticelement in which the magnetization free layer is made of the amorphousferromagnetic material behaves stably when the magnetization directionthereof is inverted and exhibits excellent magnetic characteristics.Thus, the magnetic element exhibits excellent switching characteristicswhen the TMR element is applied to a magnetic memory device such as anMRAM.

[0062] However, when the amorphous ferromagnetic material for use withthe magnetization free layer is heated up to temperature higher than itscrystallization temperature, the magnetic characteristic of the magneticelement is deteriorated and cannot exhibit excellent magneticcharacteristic. The semiconductor circuit process needs processes whichrequire annealing with temperature higher than 350° C.

[0063] For this reason, the magnetization free layer is made of anamorphous ferromagnetic material having crystallization temperaturehigher than at least 623 K (350° C.), thereby decreasing damages exertedupon the magnetic characteristics of the magnetization free layer due toheat generated from the semiconductor circuit process. As a result,affinity of the TMR element with the semiconductor circuit process canbe improved.

[0064] Alloy-based amorphous ferromagnetic materials containing any onekind or more than two kinds of B, Si, C, P, Al, Ge, Ti, Nb, Ta, Zr, Morelative to Fe, Ni, Co which exhibit ferromagnetic properties by simplesubstance may be available as amorphous ferromagnetic materials havingcrystallization temperature higher than 623 K. Since it is generallyconsidered that crystallization temperatures of amorphous alloys ofdesired combinations and amorphous alloys containing other elements,e.g., rare earth elements, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb, Lu and amorphous alloys containing V, Nb, Ta, Cr,Mo, W which are high-melting point metals as simple substance tend torise, they are suitable for being added to the amorphous ferromagneticmaterial so long as addition of such amorphous alloy does not hinderamorphous formation ability.

[0065] When a material-base composed of Co, Fe, Si and B, for example,is selected as the amorphous ferromagnetic material, dependence existsbetween crystallization temperature of the amorphous ferromagneticmaterial and its composition ratio (ratio between Fe-group element andadditive element). When B, Si are added to Fe—Co alloy, for example, ifB is added to the above alloy alone, then the amorphous structure isadded to the alloy wherein B added amount falls within a range of from10 to 30 atomic %.

[0066] However, the crystallization temperature increases as theconcentration of B increases. For example, when B of 15 atomic % isadded to Co, crystallization temperature reaches about 650 K, when 20atomic % is added, crystallization temperature reaches about 660 K, andwhen 27 atomic % is added, crystallization temperature reaches about 700K.

[0067] When B and Si are both added to cobalt, the crystallizationtemperature rises much more. For example, when B of 20 atomic % and Siof 10 atomic % are added to cobalt, the crystallization temperaturerises up to about 800 K.

[0068] As described above, an alloy composition of Co, Fe, Si, B has anoptimum range. Therefore, excepting inevitable impurity elements,amorphous ferromagnetic materials which at least one of the magneticlayers contains are composed of a composition formulaFe_(w)Co_(x)Si_(y)B_(z) (in this composition formula, w, x, y and zexpress atomic % and w+x+y+z=100), and therefore, 5≦w≦45, 35≦x≦85,0≦y≦20 and 10≦z≦30 should preferably be satisfied.

[0069] This optimum range of alloy composition will be described indetail below.

[0070] In the material base composed of Co, Fe, Si and B, the preferableadded amount of Si and the preferable added amount of B are as follows.

[0071] When the added amount of B is less than 10 atomic %, since theamorphous structure is difficult to be formed and the crystallizationtemperature reaches about 600 K, thermal stability of amorphoussubstance phase is low. With respect to the magnetic characteristics, amagnetic characteristic of an Fe—Co alloy which becomes a base materialreflects considerably and only gentle improvement and effect can beachieved.

[0072] Accordingly, the amorphous ferromagnetic material should containB of greater than 10 atomic %. In particular, in order to obtaincrystallization temperature higher than 623 K by addition of only B, theadded amount of B should increase in excess of 20 atomic %.

[0073] On the other hand, the added amount of B should preferably bemade under 30 atomic %. If the added amount of B exceeds 30 atomic %,then the crystallization temperature is lowered and the amorphoussubstance phase becomes difficult to be formed. More specifically,maximum crystallization temperature exists in a relationship between theadded amount of B and the crystallization temperature.

[0074] Whereas, when both of B and Si are added to the amorphousferromagnetic material, if the total amount of the two added amounts is30 atomic %, then high crystallization temperature can be obtained. Forexample, when the added amount of B is 15 atomic % and the added amountof Si is 15 atomic %, crystallization temperature as high as about 800 Kcan be obtained. Since the effect achieved by the addition of Si can beachieved, even when the added amount of B is decreased, similar effectscan be achieved by the addition. However, the maximum crystallizationtemperature exists in the relationship between the added amount of Siand crystallization temperature. For example, when the added amount of Bfalls within a range of from 10 to 30 atomic %, the maximumcrystallization temperature exists in a range in which the added amountof Si falls within a range of from 10 to 15 atomic %. If the addedamount exceeds 15 atomic %, then the crystallization temperature beginsto decrease in accordance with the increase of the added amount. Forexample, if the added amount of Si is 20 atomic %, then thecrystallization temperature becomes lower than that obtained when theadded amount is 15 atomic %. Thus, the crystallization temperaturereaches the crystallization temperature ranging of from 750 to 800 K andthe magnetic element becomes difficult to have an amorphous structure.Accordingly, it is desired that the added amount of Si should be lessthan 20 atomic %.

[0075] As described above, the added amount of B should preferably beselected in a range of from 10 to 30 atomic %, and the added amount ofSi should preferably be selected in a range of from 0 to 20 atomic %.More preferably, the added amount of B should be selected in a range offrom 10 to 20 atomic %, and the added amount of Si should be selected ina range of from 5 to 15 atomic %. When the added amount is selected inthe above-mentioned range, there can be obtained the amorphousferromagnetic material having high crystallization temperature rangingof from about 750 K to 830 K, and hence the amorphous ferromagneticmaterial may have soft magnetic characteristics which are required asthose of the magnetization free layer of the TMR element.

[0076] Of base alloys, a CoFe alloy of alloys has the followingpreferable composition ratio between Co and Fe.

[0077] In order to realize a high TMR ratio, in the Co—Fe ratio, thealloy should preferably be mainly composed of Co, i.e., shouldpreferably contain Co of which content is greater than 50 atomic %. Ifthe alloy is mainly composed of Fe, i.e., should contain Fe of whichcontent is greater than 50 atomic %, then coercive force increases, andhence the magnetization direction becomes difficult to be inverted.Thus, the resultant amorphous ferromagnetic material becomes unsuitablefor use with a magnetization free layer of a miniscule TMR element whosesize is in the order of sub-microns.

[0078] However, if the amount of Fe is small, then spin polarizabilitydecreases and a sufficient magnetoresistive changing rate cannot beobtained so that the signal output from the TMR element decreases.

[0079] Then, in order to obtain a sufficient magnetoresistive changingrate, at least the Fe content should be selected to be greater than 5atomic %.

[0080] As described above, the Fe content in the CoFe alloy shouldpreferably be selected in a range of from 5 atomic % to 50 atomic %.

[0081] Also, the alloy which becomes the base of the amorphousferromagnetic material may contain Ni in addition to Co, Fe.

[0082] Even when the alloy contains Ni, while increase of coercive forceis being suppressed, a satisfactory TMR ratio can be maintained and arectangle property of an R—H curve can be improved.

[0083] Then, the Ni content also has an optimum range, and hence the Nicontent should preferably be selected in a range of from 0 atomic % to35 atomic %. The reason for this is that, if the Ni content exceeds 35atomic %, coercive force decreases too much so that it becomes difficultto control operations of the TMR element.

[0084] As described above, except inevitable impurity elements, theferromagnetic material comprising at least one of the ferromagneticlayers 5. 7 is comprised of composition formulaFe_(a)Co_(b)Ni_(c)B_(d)Si_(e) (in the composition formula, a, b, c, dand e express atomic % and a+b+c+d+e=100), and 5≦a≦45, 35≦b≦85, 0≦c≦35,10≦d≦30, 0≦e≦20 should preferably be satisfied.

[0085] Then, of this composition range, amorphous ferromagnetic materialof composition in which crystallization temperature becomes higher than623 K may be used.

[0086] Although the aforementioned effect can be achieved when theamorphous ferromagnetic material with the above-mentionedcrystallization temperature higher than 623 k is applied to one of orboth of the magnetization free layer 7 and the magnetization fixed layer5, if the above amorphous ferromagnetic material is applied to, inparticular, the magnetization free layer 7, the effects can be achievedmore remarkably.

[0087] It is needless to say that any materials which are generally usedin this kind of magnetoresistive effect element can be used asferromagnetic layers other than the ferromagnetic layers containing theamorphous ferromagnetic material having crystallization temperaturehigher than 623 K.

[0088] According to the above-mentioned embodiment, since at least oneof the magnetization fixed layer 5 and the magnetization free layer 7that are the pair of ferromagnetic layers comprising the ferromagnetictunnel junction 9 contains the amorphous ferromagnetic material havingcrystallization temperature higher than 623 K, the magnetic element hasexcellent magnetic characteristic such as a TMR ratio (magnetoresistivechanging rate) by the amorphous ferromagnetic material and hence aheat-resisting property of the amorphous ferromagnetic material isimproved. Therefore, even when the magnetic element is annealed attemperature of about 623 K (300° C.) of a semiconductor circuit processin the manufacturing process, the magnetic characteristic such as theTMR ratio can be prevented from being deteriorated.

[0089] The present invention is not limited to the TMR element 1 inwhich the magnetization fixed layer 5 and the magnetization free layer 7shown in FIG. 1 are composed of single layers, respectively.

[0090] As shown in FIG. 2, for example, effects of the present inventioncan be achieved even when the magnetic element has a syntheticferrimagnet structure in which a magnetization fixed layer 5 includes anon-magnetic conductive layer 5 c sandwiched by first and secondmagnetization fixed layers 5 a and 5 b.

[0091] In a TMR element 10 shown in FIG. 2, the first magnetizationfixed layer 5 a adjoins with the antiferromagnetic layer 4, and thefirst magnetization fixed layer 5 a is given strong magnetic anisotropyof one direction by exchange interaction acting on these two layers.Also, the second magnetization fixed layer 5 b is opposed to themagnetization free layer 7 through the tunnel barrier layer 6, and thespin direction thereof is compared with that of the magnetization freelayer 7 to become a ferromagnetic layer directly concerning an MR ratio.Thus, the second magnetization fixed layer is referred to as a“reference layer”.

[0092] Materials such as Ru, Rh, Ir, Cu, Cr, Au and Ag are available asthe material for use in the non-magnetic dielectric layer 5 c having thelamination layer structure. In the TMR element 10 shown in FIG. 2, sinceother layers have structures substantially similar to those of the TMRelement 1 shown in FIG. 1, their elements and parts are denoted by theidentical reference numerals, and therefore need not be described indetail.

[0093] Also in the TMR element 10 having this synthetic ferrimagnetstructure, at least one of the magnetization fixed layer 5 and themagnetization free layer 7 contains the amorphous ferromagnetic materialwith crystallization temperature higher than 623 K, whereby aheat-resisting property can be improved and a high TMR ratio can bemaintained even after it has been annealed at about 350° C. in asuitable process such as a semiconductor process similarly to the TMRelement 1 shown in FIG. 1.

[0094] While the TMR elements (tunnel magnetoresistive effect elements)1, 10 are used as the magnetoresistive effect element in theabove-mentioned embodiment, the present invention can also be applied toother magnetoresistive effect element having an arrangement in which apair of ferromagnetic layers are opposed to each other through anintermediate layer to cause an electric current to flow in the directionperpendicular to the layer surface to obtain magnetoresistive change.

[0095] For example, the present invention can also be applied to a giantmagnetoresistive effect element (GMR element) using a non-magneticconductive layer such as Cu as an intermediate layer to cause anelectric current to flow in the direction perpendicular to the layersurface to obtain magnetoresistive effect, i.e., so-called CPP type GMRelement.

[0096] Further, in the TMR element of the present invention, materialsof the magnetization fixed layer and the antiferromagnetic body, theexistence of the antiferromagnetic material layer and the existence ofthe synthetic ferrimagnet structure on the magnetization fixed layerside can be variously modified without losing the essence of the presentinvention.

[0097] The magnetoresistive effect element such as the above-mentionedTMR elements 1, 10 is suitable for use with a magnetic memory devicesuch as an MRAM. The MRAM using the TMR element according to the presentinvention will be described below with reference to the drawings.

[0098] A cross-point type MRAM array having the TMR element according tothe present invention is shown in FIG. 3. This MRAM includes a pluralityof word lines WL and a plurality of bit lines BL perpendicular to theseword lines WL, and also includes a memory cell 11 having the TMR elementof the present invention at an intersecting point between the word lineWL and the bit line BL. More specifically, in this MRAM array, 3×3memory cells are disposed in a matrix fashion.

[0099] The TMR element for use with the MRAM array is not limited to theTMR element 1 shown in FIG. 1 and may be applied to othermagnetoresistive effect element having any arrangement to cause anelectric current to flow in the direction perpendicular to the layersurface to obtain magnetoresistive change, such as the TMR element 10having the synthetic ferrimagnet structure shown in FIG. 2 so long asmore than one layer of the ferromagnetic layer may contain amorphousferromagnetic material having crystallization temperature higher than623 K.

[0100] One memory cell is picked up from a large number of memory cellsof a memory element and its cross-sectional structure is shown in FIG.4.

[0101] As shown in FIG. 4, each memory cell 11 includes a siliconsubstrate 12, for example, on which there is formed a transistor 16composed of a gate electrode 13, a source region 14 and a drain region15. The gate electrode 13 comprises a read word line Wl1. A write wordline (equivalent to the aforementioned word line) WL2 is formed on thegate electrode 13 through an insulating layer. A contact metal 17 isconnected to the drain region 15, and an underlayer 18 is furtherconnected to the contact metal 17. The TMR element 1 according to thepresent invention is formed on this underlayer 18 at its positioncorresponding to the upper portion of the write word line WL2. A bitline (equivalent to the aforementioned bit write line) BL which isperpendicular to the word lines WL1 and WL2 is formed on this TMRelement 1. The underlayer 18 plays a role of electrically connecting theTMR element 1 and the drain region 15, which are placed at differentpositions on the plane, and is therefore referred to as a “bypass”.

[0102] This memory cell further includes interlayer insulators 19 and 20for use in insulating the respective word lines WL1, WL2 and the TMRelement 1 and a passivation film (not shown) for protecting the whole ofthe memory cell.

[0103] Since this MRAM uses the TMR element 1 having the arrangement inwhich at least one of the ferromagnetic layers of the magnetizationfixed layer 5 and the magnetization free layer 7 contains the amorphousferromagnetic material with crystallization temperature higher than 623K, a heat-resisting property of the ferromagnetic layer of the TMRelement 1 can be improved, the TMR ratio of the TMR element 1 can besuppressed from being deteriorated due to annealing and this element hashigh TMR ratio. Hence, the TMR element 1 generates an excellent output,a high resistance state and a low resistance state can be distinguishedfrom each other easily when information is read out from the memorycell, and an error rate can be decreased. Thus, this memory cell has asatisfactory read characteristic and a stability of memory operation canbe improved considerably.

INVENTIVE EXAMPLES

[0104] Specific inventive examples to which the present invention can beapplied will be described below with reference to the results ofexperiments.

[0105] Although the MRAM has a switching transistor 16 other than theTMR element 1 as shown in FIG. 4, in these inventive examples, in orderto examine TMR characteristics, characteristics of a wafer in which onlya ferromagnetic tunnel junction is formed as shown in FIGS. 5 and 6 weremeasured and estimated.

Experiment 1

[0106] First, magnetic characteristics of magnetic elements having theferromagnetic layers comprising the ferromagnetic tunnel junction, i.e.,the magnetization fixed layer and the magnetization free layer beingformed of crystal ferromagnetic materials or amorphous ferromagneticmaterials were examined.

[0107] <Sample 1>

[0108] As shown in FIGS. 5 and 6, a structure having a substrate 21 witha word line WL and a bit line BL disposed thereon at a right angle and aTMR element 22 formed at a portion in which these word line WL and bitline BL cross each other was manufactured as a characteristic estimationelement TEG (Test Element Group). This TEG has an arrangement in whichthe TMR element 22 is shaped like an ellipse with a minor axis of 0.5 μmand a major axis of 1.0 μm, terminal pads 23, 24 are respectively formedat both ends of the word line WL and the bit line BL and in which theword line WL and the bit line BL are electrically insulated from eachother by insulating films 25, 26 made of Al₂O₃.

[0109] More specifically, the TEG shown in FIGS. 5 and 6 wasmanufactured as follows.

[0110] First, there was prepared a 0.6 mm-thick silicon substrate 21with a heat oxide film (having a thickness of 2 μm) deposited on thesurface thereof.

[0111] Next, after a word line material has been deposited on thissubstrate 21 and masked by photolithography, other portion than the wordline was selectively etched by Ar laser plasma and thereby the word lineWL was formed. At that time, other area than the word line WL was etchedup to the depth of 5 nm of the substrate 2.

[0112] After that, an insulating film 26 was formed so as to cover theword line WL and the surface was made flat by planarization.

[0113] Subsequently, the TMR element 22 having the following layerarrangement was manufactured by well-known lithography and etching. Inthis layer arrangement, the left-hand side of slash indicates thesubstrate side and numerical values within the parentheses indicate filmthicknesses.

Ta(3 nm)/PtMn(20 nm)/Co₇₅Fe₂₅(2.5 nm)/Ru(0.8 nm)/Co₇₅Fe₂₅(3.0 nm)/Al(1nm)−O_(x)/Co₇₅Fe₂₅(2.5 nm)/Ta(5 nm)

[0114] The Al—O_(x) film of the tunnel barrier layer 6 was formed byplasma-oxidizing a metal Al film with plasma from ICP (inducted couplingplasma) at oxygen/argon flow rate of 1:1 and chamber gas pressure of 0.1mTorr after the metal Al film having a thickness of 1 nm has beendeposited by a DC sputtering method. An oxidation time may be changeddepending upon ICP plasma output, and it was selected to be 30 secondsin this inventive example.

[0115] Other films than the Al—O_(x) film of the tunnel barrier layer 6were deposited by a DC magnetron sputtering method.

[0116] Next, the resultant product was annealed by annealing at 270° C.for 4 hours in the magnetic field of 10 keOe by a field anneal furnace,and a ferromagnetic tunnel junction 9 was formed by normalizing-annealof a PtMn layer which is an antiferromagnetic layer.

[0117] After that, the TMR element 22 having the flat surface patternshown in FIG. 5 was formed by patterning the TMR element 22 and theinsulating film 26 disposed under this element.

[0118] Further, an insulating film 25 having a thickness of about 100 nmwas deposited by sputtering the Al₂O₃ film and the bit line BL and theterminal pad 24 were formed by photolithography, thereby resulting inthe TEG shown in FIGS. 5 and 6 being obtained.

[0119] <Sample 2>

[0120] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 22 was changed as follows.

Ta(3 nm)/PtMn(20 nm)/Co₇₅Fe₂₅(2.5 nm)/Ru(0.8 nm)/Co₇₅Fe₂₅(3.0 nm)/Al(1nm)−O_(x)/Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4 nm)/Ta(5 nm)

[0121] <Sample 3>

[0122] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 22 was changed as follows.

Ta(3 nm)/PtMn(20 nm)/Co₇₅Fe₂₅(2.5 nm)/Ru(0.8 nm)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4.5nm)/Al(1 nm)−O_(x)/Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4 nm)/Ta(5 nm)

[0123] <Sample 4>

[0124] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 22 was changed as follows.

Ta(3 nm)/PtMn(20 nm)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4 nm)/Ru(1.0nm)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4.5 nm)/Al(1 nm)−O_(x)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4nm)/Ta(5 nm)

[0125] <Sample 5>

[0126] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 22 was changed as follows.

Ta(3 nm)/PtMn(20 nm)/Co₇₅Fe₂₅(3 nm)/Al(1 nm)−O_(x)/Co₇₅Fe₂₅(3 nm)/Ta(5nm)

[0127] While the samples 1 to 4 had the layer arrangement in which themagnetization fixed layer has the synthetic ferrimagnet structure, thelayer arrangement of this sample 5 does not have the syntheticferrimagnet structure.

[0128] <Sample 6>

[0129] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 22 was changed as follows.

Ta(3 nm)/PtMn(20 nm)/Co₇₅Fe₂₅(3 nm)/Al(1nm)−O_(x)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4.5 nm)/Ta(5 nm)

[0130] <Sample 7>

[0131] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 2 was changed as follows.

Ta(3 nm)/PtMn(20 nm)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4.5 nm)/Al(1nm)−O_(x)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4.5 nm)/Ta(5 nm)

[0132] <Sample 8>

[0133] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 22 was changed as follows.

Ta(20 nm)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4 nm)/Al(1 nm)−O_(x)/Co₇₅Fe₂₅(3 nm)/Ru(1.0nm)/Co₇₅Fe₂₅(3 nm)/PtMn(20 nm)/Ta(5 nm)

[0134] More specifically, this sample 8 has an arrangement in which themagnetization free layer is formed on the substrate side, themagnetization fixed layer side having the synthetic ferrimagnetstructure.

[0135] <Sample 9>

[0136] A TEG was obtained similarly to the sample 1 except that thelayer arrangement of the TMR element 22 was changed as follows.

Ta(20 nm)/(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀(4 nm)/Al(1nm)−O_(x)/(Co₉₀Fe₁₀)_(7@)Si₁₀B₂₀(4 nm)/Ru(1.0 nm)/Co₇₅Fe₂₅(3.0nm)/PtMn(20 nm)/Ta(5 nm)

Experiment 2

[0137] The magnetization fixed layer had a synthetic ferrimagnetstructure comprising two layers of CoFe and Ru, and the magnetizationfree layer was formed as a ferromagnetic layer having a composition inwhich Si or B was added to CoFe. Then, optimum ranges of the addedamount of B and the added amount of Si were checked.

[0138] <Sample 10>

[0139] The layer arrangement of the TMR element 22 was selected to bethe following layer arrangement (1).

Ta(3 nm)/PtMn(20 nm)/Co₇₅Fe₂₅(2.5 nm)/Ru(0.8 nm)/Co₇₅Fe₂₅(3.0 nm)/Al(1nm)−O_(x)/(Co₉₀Fe₁₀)_(100-y-z)Si_(y)B_(z)(4 nm)/Ta(5 nm)  (1)

[0140] In the above-described layer arrangement (1), y and z of(Co₉₀Fe₁₀)_(100-x-y)Si_(y)B_(z) indicate composition ratios of atomic %and (Co₉₀Fe₁₀) within the parenthesis shows that Co and Fe have acomposition ratio of 90:10. If y=10 atomic % and z=10 atomic % areestablished, then (Co₉₀Fe₁₀)₈₀Si₁₀B₁₀ is satisfied. This indicates thatCoFe alloy having a composition ratio of Co:Fe=90 atomic % 10 atomic %has 80 atomic % and has a composition ratio in which Si is 10 atomic %and B is 10 atomic %. Accordingly, a composition ratio of each elementexpresses Co₇₂Fe₈Si₁₀B₁₀.

[0141] Then, this sample 10 has y=0 and z=10 atomic %, i.e., compositionof (Co₉₀Fe₁₀)₉₀B₁₀ in the above-described layer arrangement (1). Exceptfor the above-described composition, a TEG was obtained similarly to thesample 1.

[0142] <Sample 11>

[0143] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=0 and z=15 atomic %,i.e., (Co₉₀Fe₁₀)₈₅B₁₅.

[0144] <Sample 12>

[0145] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=0 and z=20 atomic %,i.e., (Co₉₀Fe₁₀)₈₀B₂₀.

[0146] <Sample 13>

[0147] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=0 and z=25 atomic %,i.e., Co₉₀Fe₁₀)₇₅B₂₅.

[0148] <Sample 14>

[0149] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=0 and z=30 atomic %,i.e., (Co₉₀Fe₁₀)₇₀B₃₀.

[0150] <Sample 15>

[0151] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=0 and z=35 atomic %,i.e., (Co₉₀Fe₁₀)₆₅B₃₅.

[0152] <Sample 16>

[0153] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=2.5 atomic % and z=15atomic %, i.e., (Co₉₀Fe₁₀)_(82.5)Si_(2.5)B₁₅.

[0154] <Sample 17>

[0155] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=2.5 atomic % and z=20atomic %, i.e., (Co₉₀Fe₁₀)_(77.5)Si_(2.5)B₂₀.

[0156] <Sample 18>

[0157] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=5 atomic % and z=10atomic %, i.e., (Co₉₀Fe₁₀)₈₅Si₅B₁₀.

[0158] <Sample 19>

[0159] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=5 atomic % and z=15atomic %, i.e., (Co₉₀Fe₁₀)₈₀Si₅B₁₅.

[0160] <Sample 20>

[0161] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=5 atomic % and z=20atomic %, i.e., (Co₉₀Fe₁₀)₇₅Si₅B₂₀.

[0162] <Sample 21>

[0163] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=5 atomic % and z=25atomic %, i.e., (Co₉₀Fe₁₀)₇₀Si₅B₂₅.

[0164] <Sample 22>

[0165] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=10 atomic % and z=0,i.e., (Co₉₀Fe₁₀)₉₀Si₁₀.

[0166] <Sample 23>

[0167] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=10 atomic % and z=5atomic %, i.e., (Co₉₀Fe₁₀)₈₅Si₁₀B₅.

[0168] <Sample 24>

[0169] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=10 atomic % and z=10atomic %, i.e., (Co₉₀Fe₁₀)₈₀Si₁₀B₁₀.

[0170] <Sample 25>

[0171] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=10 atomic % and z=15atomic %, i.e., (Co₉₀Fe₁₀)₇₅Si₁₀B₁₅.

[0172] <Sample 26>

[0173] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=10 atomic % and z=20atomic %, i.e., (Co₉₀Fe₁₀)₇₀Si₁₀B₂₀.

[0174] <Sample 27>

[0175] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=10 atomic % and z=25atomic %, i.e., (Co₉₀Fe₁₀)₆₅Si₁₀B₂₅.

[0176] <Sample 28>

[0177] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=10 atomic % and z=30atomic %, i.e., (Co₉₀Fe₁₀)60Si₁₀B₃₀.

[0178] <Sample 29>

[0179] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=15 atomic % and z=5atomic %, i.e., (Co₉₀Fe₁₀)₈₅Si₁₅B₅.

[0180] <Sample 30>

[0181] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=15 atomic % and z=10atomic %, i.e., (Co₉₀Fe₁₀)₇₅Si₁₅B₁₀.

[0182] <Sample 31>

[0183] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=15 atomic % and z=15atomic %, i.e., (Co₉₀Fe₁₀)₇₀Si₁₅B₁₅.

[0184] <Sample 32>

[0185] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=15 atomic % and z=20atomic %, i.e., (Co₉₀Fe₁₀)₆₅Si₁₅B₂₀.

[0186] <Sample 33>

[0187] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=15 atomic % and z=25atomic %, i.e., (Co₉₀Fe₁₀)₆₀Si₁₅B₂₅.

[0188] <Sample 34>

[0189] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=20 atomic % and z=0,i.e., (Co₉₀Fe₁₀)₈₀Si₂₀.

[0190] <Sample 35>

[0191] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=20 atomic % and z=5atomic %, i.e., (Co₉₀Fe₁₀)₇₅Si₂₀B₅.

[0192] <Sample 36>

[0193] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=20 atomic % and z=10atomic %, i.e., (Co₉₀Fe₁₀)₇₀Si₂₀B₁₀.

[0194] <Sample 37>

[0195] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=20 atomic % and z=15atomic %, i.e., (Co₉₀Fe₁₀)₆₅Si₂₀B₁₅.

[0196] <Sample 38>

[0197] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=20 atomic % and z=20atomic %, i.e., (Co₉₀Fe₁₀)₆₀Si₂₀B₂₀.

[0198] <Sample 39>

[0199] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=25 atomic % and z=5atomic %, i.e., (Co₉₀Fe₁₀)₇₀Si₂₅B₅.

[0200] <Sample 40>

[0201] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=25 atomic % and z=10atomic %, i.e., (Co₉₀Fe₁₀)₆₅Si₂₅B₁₀.

[0202] <Sample 41>

[0203] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of y=25 atomic % and z=15atomic %, i.e., (Co₉₀Fe₁₀)₆₀Si₂₅B₁₅.

Experiment 3

[0204] A magnetization free layer has a synthetic ferrimagnet structurecomprising two layers of CoFe and Ru, and a magnetization free layer wasformed as a ferromagnetic layer having a composition in which Si and Bwere added to (Co, Fe). Then, an optimum range of Fe content waschecked.

[0205] <Sample 42>

[0206] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of(Co_(100-x)Fe_(x))₇₀Si₁₀B₂₀, further x=0, i.e., a composition ofCo₇₀Si₁₀B₂₀ in the layer arrangement (1).

[0207] <Sample 43>

[0208] A TEG was obtained similarly to the sample 42 except that themagnetization free layer has a composition of x=5 atomic %, i.e., acomposition of (Co₉₅Fe₅)₇₀Si₁₀B₂₀.

[0209] <Sample 44>

[0210] A TEG was obtained similarly to the sample 42 except that themagnetization free layer has a composition of x=10 atomic %, i.e., acomposition of (Co₉₀Fe₁₀)₇₀Si₁₀B₂₀.

[0211] <Sample 45>

[0212] A TEG was obtained similarly to the sample 42 except that themagnetization free layer has a composition of x=25 atomic %, i.e., acomposition of (Co₇₅Fe₂₅)₇₀Si₁₀B₂₀.

[0213] <Sample 46>

[0214] A TEG was obtained similarly to the sample 42 except that themagnetization free layer has a composition of x=40 atomic %, i.e., acomposition of (Co₆₀Fe₄₀)₇₀Si₁₀B₂₀.

[0215] <Sample 47>

[0216] A TEG was obtained similarly to the sample 42 except that themagnetization free layer has a composition of x=50 atomic %, i.e., acomposition of (Co₅₀Fe₅₀)₇₀Si₁₀B₂₀.

[0217] <Sample 48>

[0218] A TEG was obtained similarly to the sample 42 except that themagnetization free layer has a composition of x=70 atomic %, i.e., acomposition of (Co₃₀Fe₇₀)₇₀Si₁₀B₂₀.

Experiment 4

[0219] A magnetization fixed layer has a synthetic ferrimagnet structurecomprising two layers of CoFe and Ru and a magnetization free layer wasformed as a ferromagnetic layer having a composition in which Si and Bwere added to (Co, Fe, Ni). Then, optimum ranges of Fe content and Nicontent were checked.

[0220] <Sample 49>

[0221] A TEG was obtained similarly to the sample 10 except that amagnetization free layer has a composition of(Co_(100-x-w)Fe_(x)Ni_(w))₇₀Si₁₀B₂₀, further x=6 atomic %, w=40 atomic%, i.e. , a composition of (Co₅₄Fe₆Ni₄₀)₇₀Si₁₀B₂₀.

[0222] <Sample 50>

[0223] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=15 atomic %, w=40 atomic %, i.e., acomposition of (Co₄₅Fe₁₅Ni₄₀)₇₀Si₁₀B₂₀.

[0224] <Sample 51>

[0225] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=6.5 atomic %, w=35 atomic %, i.e., acomposition of (Co_(58.5)Fe_(6.5)Ni₃₅)₇₀Si₁₀B₂₀.

[0226] <Sample 52>

[0227] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=16.25 atomic %, w=35 atomic %, i.e., acomposition of (Co_(48,75)Fe_(16.25)Ni₃₅)₇₀Si₁₀B₂₀.

[0228] <Sample 53>

[0229] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=7 atomic %, w=30 atomic %, i.e., acomposition of (Co₆₃Fe₇Ni₃₀)₇₀Si₁₀B₂₀. cl Sample 54

[0230] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=17.5 atomic %, w=30 atomic %, i.e., acomposition of (Co_(52.5)Fe17.5Ni₃₀)₇₀Si₁₀B₂₀.

[0231] <Sample 55>

[0232] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=8 atomic %, w=20 atomic %, i.e., acomposition of (Co₇₂Fe₈Ni₂₀)₇₀Si₁₀B₂₀.

[0233] <Sample 56>

[0234] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=20 atomic %, w=20 atomic %, i.e., acomposition of (Co₆₀Fe₂₀Ni₂₀)₇₀Si₁₀B₂₀.

[0235] <Sample 57>

[0236] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=9 atomic %, w=10 atomic %, i.e., acomposition (Co₈₁Fe₉Ni₁₀)₇₀Si₁₀B₂₀.

[0237] <Sample 58>

[0238] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=22.5 atomic %, w=10 atomic %, i.e., acomposition of (Co_(67.5)Fe_(22.5)Ni₁₀)₇₀Si₁₀B₂₀.

[0239] <Sample 59>

[0240] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=10 atomic %, w=0, i.e., a composition of(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀.

[0241] <Sample 60>

[0242] A TEG was obtained similarly to the sample 49 except that themagnetization free layer has x=25 atomic %, w=0, i.e., a composition of(Co₇₅Fe₂₅)₇₀Si₁₀B₂₀.

Experiment 5

[0243] A magnetization fixed layer had a synthetic ferrimagnet structurecomprising two layers of CoFe and Ru, and a magnetization free layer hada composition in which various elements were added to (Co, Fe). Then,characteristics thereof were checked.

[0244] <Sample 61>

[0245] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of Co_(70.3)Fe_(4.7)P₁₃C₇(atomic %).

[0246] <Sample 62>

[0247] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of Co₇₂Fe₃P₁₆B₆Al₁₃ (atomic%).

[0248] <Sample 63>

[0249] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition ofCo_(69.6)Fe_(4.6)Mo_(1.8)Si₈B₁₆ (atomic %).

[0250] <Sample 64>

[0251] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition ofCo_(74.3)Fe_(2.6)Mn_(3.1)Si₄B₁₆ (atomic %).

[0252] <Sample 65>

[0253] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of Co₇₀Mn₆B₂₄ (atomic %).

[0254] <Sample 66>

[0255] A TEG was obtained similarly to the sample 10 except that themagnetization free layer has a composition of Co_(81.5)Mo_(9.5)Zr₉(atomic %).

[0256] Then, TMR ratios were calculated from TEGs of the thus obtainedrespective samples 1 to 66 by the following methods. Further, amorphoussubstance phases were identified, and crystallization temperatures weremeasured.

TMR Ratio

[0257] While an ordinary magnetic memory device such as an MRAM isadapted to write information therein by inverting the magnetizationdirection of the magnetoresistive effect element with application of anelectric current magnetic field, according to this inventive example, aresistance value was measured by magnetizing the magnetoresistive effectelement with application of an external magnetic field. Morespecifically, first, an external magnetic field for inverting themagnetization direction of the magnetization free layer of the TMRelement 22 was applied to the magnetization free layer in parallel tothe easy axis of magnetization of the magnetization free layer. Amagnitude of an external magnetic field for measuring a resistance valuewas 500 Oe.

[0258] Next, at the same time the external magnetic field is applied tothe magnetization free layer in a range of from −500 Oe to +500 Oe asseen from one side of the easy axis of magnetization of themagnetization free layer, a tunnel electric current is caused to flowthrough the ferromagnetic tunnel junction while a bias voltage appliedto the terminal pad 23 of the word line WL and the terminal pad 24 ofthe bit line BL is being adjusted such that the bias voltage may reach100 mV. Resistance values obtained against respective external magneticfields at that time were measured. Then, a resistance value obtained inthe state in which the magnetization directions of the magnetizationfixed layer and the magnetization free layer are anti-parallel,resistance values being high and a resistance value obtained in thestate in which the magnetization directions of the magnetization fixedlayer and the magnetization free layer are parallel to each other,resistance values being low were calculated. Then, TMR ratios(magnetoresistive changing rates) were calculated from these resistancevalues.

Identification of Amorphous Substance Phase

[0259] Miniscule structures of ferromagnetic materials according to theinventive examples were observed by a transmission electron microscope(TEM) and an X-ray diffraction.

[0260] Since X-rays pass through a film thickness region of about 5 nmcomprising the above-mentioned ferromagnetic tunnel junction or athinner film thickness region and the film thickness in these filmthickness ranges is not sufficient to obtain diffraction patterns, aferromagnetic material single layer film with a film thickness of 500 nmhaving the same composition as that of the magnetization free layer ofeach sample was measured as a new sample for identifying the amorphoussubstance phase through X-ray diffraction and then measured. Through theX-ray diffraction patterns, only broad peaks were observed on the lowangle side and diffraction peak of crystal layer is not observed. In theTEM observation, samples from which halo rings have been observed byelectron ray diffraction images were identified as amorphous substancestructures.

Measurement of Crystallization Temperature

[0261] Crystallization temperatures were measured when resistance valueswere measured by a 4-terminal method in a vacuum anneal furnace,Although resistance values are changed considerably before and aftercrystallization, temperature at which this resistance change wasobserved clearly was normalized as “crystallization temperature”. In thelayer arrangement of the TMR element in actual practice, since it isdifficult to measure crystallization temperature of ferromagneticmaterial similarly to the X-ray diffraction, new measurement sampleshaving a film thickness of 100 nm were manufactured under the sameconditions as those in which the TMR layer arrangement is deposited assamples for use in measuring crystallization temperature.

Relationship Between TMR Layer Arrangement and Heat-Resisting Property

[0262] First, a relationship between an optimum layer arrangement and aheat-resisting property obtained when (Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ was used as anamorphous ferromagnetic material having crystallization temperaturehigher than 623 K will be described with reference to the estimatedresults of <samples 1 to 9>.

[0263] It was identified by X-ray diffraction and TEM that this(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ has an amorphous structure, and crystallizationtemperature is 800 K. In other words, this sample satisfies requirementsof the present invention and falls within the present invention.

[0264] <Sample 1> includes a magnetization fixed layer composed of aPtMn antiferromagnetic layer and a synthetic ferrimagnet structure. Acrystal ferromagnetic material Co₇₅Fe₂₅ is provided on a magnetizationfree layer, a first magnetization fixed layer (pinned layer) and asecond magnetization fixed layer (reference layer) on an Al—O_(x)insulating layer.

[0265] <Sample 2> has a magnetization fixed layer composed of a PtMnantiferromagnetic layer and a synthetic ferrimagnet structure, and a(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ is provided on a magnetization free layer on anAl—O_(x) tunnel insulating layer.

[0266] <Sample 3> has a magnetization fixed layer composed of a PtMnantiferromagnetic layer and a synthetic ferrimagnet structure, and a(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ is provided on a magnetization free layer on anAl—O_(x) tunnel insulating layer and a second magnetization fixed layer(reference layer) having a synthetic ferrimagnet structure.

[0267] <Sample 4> has a magnetization fixed layer composed of a PtMnantiferromagnetic layer and a synthetic ferrimagnet structure, and a(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ is provided on a magnetization free layer on anAl—O_(x) tunnel insulating layer, a first magnetization fixed layer(pinned layer) having a synthetic ferrimagnet structure and a secondmagnetization fixed layer (reference layer).

[0268] <Sample 5> has a magnetization fixed layer structure composed ofa PtMn antiferromagnetic layer, and a crystal ferromagnetic materialCo₇₅Fe₂₅ is provided on a magnetization free layer and a magnetizationfixed layer on an Al—O_(x) tunnel insulating layer.

[0269] <Sample 6> has a magnetization fixed layer structure composed ofa PtMn antiferromagnetic layer, and a (Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ is provided ona magnetization free layer on an Al—O_(x) tunnel insulating layer.

[0270] <Sample 7> has a magnetization fixed layer structure composed ofa PtMn antiferromagnetic layer, and (Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ is provided on amagnetization free layer and a magnetization fixed layer on an Al—O_(x)tunnel insulating layer.

[0271] <Sample 8> has a magnetization fixed layer composed of a PtMnantiferromagnetic layer and a synthetic ferrimagnet structure, amagnetization fixed layer having a synthetic ferrimagnet structure isprovided above an Al—O_(x) tunnel insulating layer and a(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ is provided on a magnetization free layer locatedunder the Al—O_(x) tunnel insulating layer.

[0272] <Sample 9> has a magnetization fixed layer composed of a PtMnantiferromagnetic layer and a synthetic ferrimagnet structure, amagnetization fixed layer having a synthetic ferrimagnet structure isprovided above an Al—O_(x) tunnel insulating layer and a(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ is provided on a magnetization free layer locatedunder the Al—O_(x) tunnel insulating layer and a magnetization fixedlayer (in this case, reference layer) on the under side of themagnetization fixed layer having the synthetic ferrimagnet structure.

[0273] With respect to the samples 1 to 9, TMR ratios of manufacturedTEGs (annealed at 270° C. for 4 hours), and TMR ratios of themanufactured TEGs that have been further annealed at 350° C. for 10hours were measured.

[0274] These measured results are shown on the table 1. TABLE 1 TMRratio (%) TMR ratio (%) obtained obtained after Layer Layer containingafter anneal at 270° C. anneal at 350° C. Sample Nos. arrangement(Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ for 4 hours for 10 hours 1 Bottom-spin None 44% 10%type, laminated layer structure 2 Bottom-spin Magnetization 54% 45%type, laminated free layer layer structure 3 Bottom-spin Referencelayer, 49% 42% type, laminated magnetization layer structure free layer4 Bottom-spin Pinned layer, 47% 42% type, laminated reference layer,layer structure magnetization free layer 5 Bottom-spin None 44% 9% type6 Bottom-spin Magnetization 50% 42% type free layer 7 Bottom-spin Pinnedlayer, 49% 41% type magnetization free layer 8 Bottom-spin Magnetization48% 40% type, laminated free layer layer structure 9 Bottom-spinMagnetization 46% 40% type, laminated free layer layer structurereference layer

[0275] As shown on the table 1, it is to be understood from comparisonsof the sample 1 with the samples 2 to 4 that, if any one layer or morethan two layers of the ferromagnetic layer of the TMR element is made ofan amorphous ferromagnetic material (Co₉₀Fe₁₀)₇₀Si₁₀B₂₀ havingcrystallization temperature higher than 623 K which falls within therange of the present invention, then an amount in which TMR ratio isdecreased by annealing at 350° C. is small and a heat-resistingefficiency can be improved.

[0276] Having considered the samples 2 to 4, it is to be noted that themagnetization free layer should preferably be made of only the amorphousferromagnetic material according to the present invention as in thesample 2 in order to obtain higher TMR ratios and that high TMR ratioscan be obtained under annealing conditions at relatively hightemperature of 350° C.

[0277] Further, from the results of the samples 5 to 7, it is to beunderstood that a heat-resisting property can be improved by using theamorphous ferromagnetic material according to the present invention tomake the ferromagnetic layer regardless of the existence of thesynthetic ferrimagnet structure.

[0278] Similarly, from the results of the samples 8 to 9, it is to beunderstood that a heat-resisting property can be improved by using theamorphous ferromagnetic material according to the present invention tomake the ferromagnetic layer even when the magnetic material has anarrangement (so-called top-spin type) in which a magnetization fixedlayer is disposed on the upper side of the tunnel insulating layer.

[0279] More specifically, if any one layer or more than two layers ofthe ferromagnetic layer are made of the amorphous ferromagnetic materialhaving crystallization temperature higher than 623 K, then regardless ofthe arrangement in which the magnetic element is of the so-calledbottom-spin type or the top-spin type, effects for improving aheat-resisting property can be achieved. Also, effects for improving aheat-resisting property can be achieved regardless of the existence ofthe synthetic ferrimagnet structure.

[0280] Accordingly, the effects of the present invention can be achievedwhen one layer or more than two layers of the ferromagnetic layer aremade of the amorphous ferromagnetic material having crystallizationtemperature higher than 623 K regardless of the existence of, inparticular, the layer arrangement of the TMR element.

[0281] From a standpoint of obtaining the highest TMR ratio, based uponthe comparison with the samples 2 to 4, it is to be understood that onlythe magnetization free layer should preferably be made of the amorphousferromagnetic material according to the present invention when themagnetic element is of the bottom-spin type. Also, from the comparisonswith the samples 2 and 6, it is to be noted that the magnetic elementshould preferably have the synthetic ferrimagnet structure. Further,from the comparisons with the samples 2 and 8, it is to be noted thatmagnetic element should preferably be of the bottom-spin type.Accordingly, it is to be understood from these results that the magneticelement should suitably be of the bottom-spin type with the syntheticferrimagnet structure and that only the magnetization free layer shouldbe made of the amorphous ferromagnetic material having crystallizationtemperature higher than 623 K.

Composition Dependences of Si and B of TMR Element Using CoFe—Si—BAmorphous Ferromagnetic Material

[0282] Any of the respective samples (samples 10 to 41) of theexperiment 2 has an arrangement in which it is of the bottom-spin typewith the synthetic ferrimagnet structure, only the magnetization freelayer being made of the ferromagnetic material containing Co, Fe, Si andB.

[0283] Crystallization temperatures of the respective samples weremeasured and measured results are shown on the table 2. FIG. 7 showsrelationships among Si content y (atomic %), B content z (atomic %) andcrystallization temperatures (K).

[0284] Samples in which measured values of crystallization temperaturesare shown by asterisks did not exhibit clear magnetoresistive change inthe measurements of crystallization temperatures. From the results ofthe X-ray diffraction and the TEM observation, it is considered thatmixed phase of crystal phase and amorphous phase or crystal phase may beobtained. These samples are shown by solid circles in FIG. 7. TABLE 2Sample Si content B content Crystallization Nos. (atomic %) (atomic %)temperature 10 0 10 600 11 0 15 650 12 0 20 660 13 0 25 680 14 0 30 70015 0 35 * 16 2.5 15 700 17 2.5 20 740 18 5 10 650 19 5 15 720 20 5 20770 21 5 25 780 22 10 0 * 23 10 5 600 24 10 10 780 25 10 15 800 26 10 20800 27 10 25 830 28 10 30 * 29 15 5 690 30 15 10 780 31 15 15 800 32 1520 820 33 15 25 * 34 20 0 * 35 20 5 700 36 20 10 750 37 20 15 800 38 2020 * 39 25 5 * 40 25 10 * 41 25 15 *

[0285] From FIG. 7, it is to be understood that the crystallizationtemperature changes depending upon the Si content and the B content andthat the Si content and the B content have optimum ranges. Then, theseadded elements have effects for improving a TMR ratio and are suitablefor use with the TMR element applied to the MRAM.

[0286] Next, with respect to the samples 10 to 41, TMR ratios(magnetoresistive changing rates) of manufactured TEGs (after annealedat 270° C. for 4 hours) were measured. Further, after the thusmanufactured TEGs have been further annealed at 350° C. for 10 hours,TMR ratios (magnetoresistive changing rates) thereof were measured andrates in which TMR ratios were deteriorated (rates in which TMR ratioswere decreased after annealing at 350°) were measured by calculation.

[0287] These measured results are shown on the table 3. Relationshipsamong the Si content y (atomic %), the B content z (atomic %) and TMRratios are shown in FIGS. 8 and 9. FIG. 8 shows TMR ratios obtained fromthe manufactured TEGs after they have been annealed at 270° C. for 4hours, and FIG. 9 shows TMR ratios obtained from the manufactured TEGsafter they have been annealed at 350° C. for 10 hours. In FIGS. 8 and 9,open and solid circles denote the same samples shown in FIG. 7. TABLE 3TMR ratio (%) TMR ratio (%) Si B obtained after obtained after Sam-content content annealing at annealing at Deterioration ple (atomic(atomic 270° C. for 350° C. for 10 rate of TMR Nos. %) %) 4 hours hoursratio (%) 10 0 10 48 15 67.4 11 0 15 49 24 51 12 0 20 54 29 46.3 13 0 2553 32 39.6 14 0 30 52 35 32.7 15 0 35 35 20 42.9 16 2.5 15 49 34 30.6 172.5 20 54 35 35.2 18 5 10 48 25 47.9 19 5 15 51 34 33.3 20 5 20 55 3536.4 21 5 25 50 35 30 22 10 0 45 15 66.7 23 10 5 47 22 53.2 24 10 10 5335 34 25 10 15 55 36 34.5 26 10 20 54 36 33.3 27 10 25 49 35 28.6 28 1030 41 25 39 29 15 5 47 32 31.9 30 15 10 55 36 34.5 31 15 15 55 36 34.532 15 20 49 35 28.6 33 15 25 42 25 40.5 34 20 0 44 20 54.5 35 20 5 47 3427.7 36 20 10 52 35 32.7 37 20 15 52 35 32.7 38 20 20 38 20 47.4 39 25 544 20 54.5 40 25 10 46 21 54.3 41 25 15 40 20 50

[0288] From the results on the table 3 and FIG. 8, it is understood thatTMR ratios can be improved by adding Si and B to the Co—Fe alloy. Inaddition, when a ferromagnetic material having an amorphous structure isused to make a magnetic element (shown by open circles), effects forincreasing TMR ratios can be achieved considerably.

[0289] On the other hand, since any of the arrangements which aredifficult to obtain amorphous structures (respective samples of sampleNos. 15, 22, 28, 33, 38, 39, 40, 41: solid circles) cannot obtainsufficient TMR ratios, these samples are not suitable for thearrangements of the TMR elements.

[0290] Further, from the results of the table 3 and FIG. 9, it is to beunderstood that the TMR ratios of the arrangements that are difficult tohave amorphous substance structures (respective samples of sample Nos.15, 22, 28, 33, 38, 39, 40, 41) are lowered considerably after annealingat 350° C. for 10 hours.

[0291] In addition, it is also to be understood that the TMR ratios ofthe arrangements (samples 10 and 23) whose crystallization temperaturesare lower than 350° C., i.e., 623 K are considerably lowered afterannealing at 350° C. for 10 hours

[0292]FIG. 10 shows a relationship between crystallization temperaturesand deteriorations rates of TMR ratios due to annealing at 350° C.

[0293] A study of FIG. 10 reveals that the deterioration rate of the TMRratio decreases as the crystallization temperature rises. As FIG. 11,which is a diagram showing a part of FIG. 10 in an enlarged-scale,shows, when the crystallization temperature is higher than 623 K (350°C.), the deterioration rate of the TMR ratio decreases under 60%, andeffects achieved by high crystallization temperatures become remarkable.

[0294] Accordingly, the composition range containing materialcompositions of the arrangements whose crystallization temperatures arehigher than 350° C., i.e., 623 K (samples 11 to 14, 16 to 21, 23 to 27,29 to 32, 35 to 37) is suitable. This range is illustrated as an areaencircled by a bold line in FIG. 12 as a range of the Si content y(atomic %) and the B content z (atomic %). Open circles and solidcircles are the same as those of FIG. 7 and numerals attached to opencircles and solid circles indicate sample Nos.

Co and Fe Composition Dependence of TMR Element Using CoFe—Si—BAmorphous Ferromagnetic Material

[0295] Each of samples (samples 42 to 48) of the experiment 3 is of thebottom-spin type, and has a synthetic ferrimagnet structure, only themagnetization free layer being made of amorphous ferromagnetic material.Then, the Si content was fixed to 10 atomic %, the B content was fixedto 20 atomic %, and the composition ratio of Co and Fe was changed.

[0296] Crystallization temperatures of these respective samples weremeasured, and measured results of Co composition ratios, Fe compositionratios in CoFe of respective samples and measured results ofcrystallization tempertures were shown on the table 4. TABLE 4 SampleCrystallization Nos. Co/(Co + Fe) (%) Fe/(Co + Fe) (%) temperature (K)42 100 0 810 43 95 5 800 44 90 10 800 45 75 25 800 46 60 40 810 47 50 50800 48 30 70 800

[0297] From the table 4, it is to be understood that the crystallizationtemperatures are not changed substantially even when the compositionratios of Co and Fe were changed.

[0298] Next, with respect to these samples 42 to 48, TMR ratios(magnetoresistive changing rates) of manufactured TEGs (that have beenannealed at 270° C. for 10 hours) were measured, and TMR ratios(magnetoresistive changing rates) obtained from manufactured TEGs afterthey have been further annealed at 350° C. for 10 hours also weremeasured. Deterioration rates of TMR ratios were also obtained bycalculation.

[0299] These measured results were shown on the table 5. TABLE 5 TMRratio (%) TMR ratio (%) Co/ obtained after obtained after (Co + Fe/annealing at annealing at Deterioration Sample Fe) (Co + 270° C. for350° C. for rate (%) of Nos. (%) Fe) (%) 4 hours 10 hours TMR ratio 42100 0 40 28 30 43 95 5 49 34 30.6 44 90 10 54 36 33.3 45 75 25 58 3834.5 46 60 40 56 36 35.7 47 50 50 50 35 30 48 30 70 42 28 33.3

[0300] From the table 5, it is to be understood that the crystallizationtemperatures of these samples 42 to 48 are higher than 800 K, TMR ratiosthereof are lowered lesser after they have been annealed at 350° C. for10 hours and that their TMR ratios are lowered lesser than thoseobtained when the crystallization temperature of thepreviously-described sample 10 is lower than 623 K.

[0301] However, the TMR ratios of the samples 42 and 48 are under 45% atthe stage in which they are annealed at 270° C. for 4 hours. In otherwords, the TMR ratios of these samples are too small, and hence thesesamples are not suitable for use as the magnetic memory device such asthe MRAM.

[0302] Accordingly, it becomes clear that, in the ferromagnetic materialmade of Co, Fe, Si, B, more preferable abundances of Co and Fe are50≦Co/(Co+Fe)≦95 and 5≦Fe/(Co+Fe)≦50 relative to the total content ofCo+Fe.

Co, Fe and Ni Composition Dependences of TMR Element Using CoFeNi—Si—BAmorphous Ferromagnetic Material

[0303] Any one of respective samples (samples 49 to 60) of theexperiment 4 is of the bottom-spin type and has the lamination layerstructure, only the magnetization free layer thereof being made of anamorphous ferromagnetic material. Then, changes of characteristics werechecked when the composition ratio of Fe and composition ratio of Niwere changed while the Si content was fixed to 10 atomic % and the Bcontent was fixed to 20 atomic %.

[0304] Crystallization temperatures of respective samples were measured,and the Co content, the Fe content, the Ni content in the respectivesamples (Co, Fe, Ni) and measured results of crystallizationtemperatures are shown on the table 6. TABLE 6 Sample Co Fe NiCrystallization Nos. content (%) content (%) content (%) temperature (K)49 54 6 40 820 50 45 15 40 820 51 58.5 6.5 35 820 52 48.75 16.25 35 82053 63 7 30 810 54 52.5 17.5 30 820 55 72 8 20 810 56 60 20 20 810 57 819 10 810 58 67.5 22.5 10 810 59 90 10 0 800 60 75 25 0 800

[0305] From the table 6, it is to be understood that these samples 49 to60 do not depend upon the composition ratio of Ni too much and thattheir crystallization temperatures are all higher than 800 K.

[0306] With respect to the samples 49 to 60, TMR ratios(magnetoresistive changing rates) of manufactured TEGs (annealed at 270°C. for 4 hours) were measured, and TMR ratios (magnetoresistive changingrate) were also measured after these samples have been further annealedat 350° C. for 10 hours. In addition, deterioration rates of TMR ratiosalso were obtained by calculation.

[0307] These results were shown on the table 7. TABLE 7 TMR ratio (%)TMR ratio (%) obtained after obtained after annealing at annealing atDeterioration Sample Co content Fe content Ni content 270° C. for 350°C. for rate (%) of TMR Nos. (%) (%) (%) 4 hours 10 hours ratio 49 54 640 38 25 34.2 50 45 15 40 40 26 35 51 58.5 6.5 35 45 30 33.3 52 48.7516.25 35 46 30 34.8 53 63 7 30 46 30 34.8 54 52.5 17.5 30 48 32 33.3 5572 8 20 47 31 34 56 60 20 20 50 33 34 57 81 9 10 52 34 34.6 58 67.5 22.510 54 36 33.3 59 90 10 0 54 36 33.3 60 75 25 0 58 38 34.5

[0308] From the table 7, it is clear that the ctystallizationtemperatures of these samples 49 to 60 are higher than 800 K,deterioration rates of TMR ratios obtained after samples have beenannealed at 350° C. for 10 hours were small, deterioration rates of TMRratios of these samples being smaller than those obtained when thecrystallization temperature of the previously-described sample 10 or thelike is lower than 623 K.

[0309] However, the TMR ratios of the samples 49 and 50 are lower than45% at the stage in which they are annealed at 270° C. for 4 hours. Inother words, their TMR ratios are too small, and hence these samples arenot suitable for use with the magnetic memory device such as the MRAM.

[0310] Accordingly, it is to be understood that in the ferromagneticmaterial made of Co, Fe, Ni, Si, B, more preferable Ni abundance fallswithin a range of 0≦Ni/(Co+Fe+Ni)≦35 relative to the total content ofCo+Fe+Ni.

Added Element Dependence Obtained When Si,B and Other Elements Are Addedto the Base Alloy

[0311] Any one of respective samples (samples 61 to 66) of theexperiment 5 is of the bottom-spin type and has the syntheticferrimagnet structure, only the magnetization free layer being made ofthe amorphous ferromagnetic material. Then, characteristics weremeasured when chemical elements selected from Si, B, P, C, Al, Mo, Mn,Zr are added to a ferromagnetic alloy of which fundamental compositionis CoFe comprising the magnetization free layer.

[0312] Crystallization temperatures of respective samples were measured,and compositions of respective samples and measured results ofcrystallization temperatures are shown on the table 8. TABLE 8Composition of material of Crystallization Sample Nos. magnetizationfree layer temperature (K) 61 Co_(70.3)Fe_(4.7)P₁₃C₇ 740 62Co₇₂Fe₃P₁₆B₆A₁₃ 750 63 Co_(69.6)Fe_(4.6)Mo_(1.8)Si₈B₁₆ 790 64Co_(74.3)Fe_(2.6)Mn_(3.1)Si₄B₁₆ 580 65 Co₆₃Fe₇Mn₆B₂₄ 740 66Co₇₃Fe_(8.5)Mo_(9.5)Zr_(9.0) 840

[0313] From the table 8, it is to be noted that, while the sample 64 haslow crystallization temperature under 623 K, other samples exhibit highcrystallization temperatures.

[0314] Next, with respect to the samples 61 to 66, TMR ratios(magnetoresistive changing rates) of manufactured TEGs (after annealedat 270° C. for 4 hours) were measured, and TMR ratios (magnetoresistivechanging rates) of manufactured TEGs obtained after they have beenfurther annealed at 350° C. for 10 hours were also measured. Inaddition, the deterioration rates of the TMR ratios also were obtainedby calculation.

[0315] These measured results are shown on the table 9. TABLE 9 TMRratio (%) obtained after TMR ratio (%) obtained after Sample annealingat 270° C. annealing at 350° C. Deterioration rate (%) Nos. for 4 hoursfor 10 hours of TMR ratio 61 51 31 39.2 62 46 30 34.8 63 50 34 32 64 4721 55.3 65 49 34 30.6 66 53 35 34

[0316] From the table 9, it is to be understood that deteriorations ofTMR ratios of the samples 63, 65, 66 are small after they have beenannealed at 400° C. for 0.5 hour. On the other hand, since the sample 64has low crystallization temperature under 623 K similarly to thepreviously-described sample 10, the deterioration of the TMR ratiothereof is large after it has been annealed at 350° C.

[0317] As described above, it is to be understood that similar effectsare achieved even when C, P, Al, Mo, Zr that are additives for promotingthe amorphous substance state to raise crystallization temperatures areadded to the ferromagnetic alloy in addition to Si and B.

[0318] As shown by the sample 65, other chemical elements such as Mn maybe contained in the present invention so long as resultantcrystallization temperatures are higher than 623 K.

[0319] It is needless to say that similar effects can be achieved whennot only Si, B and C, O, Al, Mo, Zr and Mn enumerated in the inventiveexamples but also semimetal elements known as metalloid elements, e.g.Ge, Ti, Nb, Ta are added to the ferromagnetic alloy. In addition, solong as one kind or more than two kinds are main components of additivesadded to (Co, Fe, Ni) ferromagnetic alloys, if crystallizationtemperatures are higher than 623 K and satisfactory TMR ratios areobtained, such metalloid elements also may be included in the scope ofthe present invention. Then, a TMR element with a satisfactoryheat-resisting property and which is best suitable for use as the MRAMcan be constructed.

[0320] A magnetoresistive effect element (TMR element) according to thepresent invention can be applied not only to the aforementioned magneticmemory device but also to a magnetic head and a hard disk drive, amagnetic sensor having this magnetic head mounted thereon and anintegrated circuit chip and further to various kinds of electronicequipment such as personal computers, personal digital assistants andmobile phones and electronic devices and the like.

[0321] The present invention is not limited to the above-mentionedembodiments and can take various arrangements without departing from thegist of the present invention.

[0322] According to the above-mentioned magnetoresistive effect elementof the present invention, since more than any one layer of theferromagnetic layers are made of the amorphous ferromagnetic materialwith the crystallization temperature higher than 623 K, themagnetoresistive changing rate can be improved by the amorphousferromagnetic material, and a magnetoresistive effect element with anexcellent heat-resisting property can be obtained.

[0323] As a result, affinity between a magnetoresistive effect elementand a semiconductor circuit manufacturing process can be improved. Thus,when the magnetoresistive effect element is applied to a magnetic memorydevice, read errors can be decreased, and excellent read characteristicscan be obtained.

[0324] Furthermore, according to the magnetic memory device of thepresent invention, it is possible to realize a magnetic memory devicecapable of solving a problem of a heat-resisting property and outputtinga large output signal and which has excellent read characteristics.

DESCRIPTION OF REFERENCE NUMERALS

[0325]1, 10, 22 . . . tunnel magnetoresistive effect element (TMRelement)

[0326]2, 21 . . . substrate

[0327]3 . . . underlayer

[0328]4 . . . antiferromagnetic layer

[0329]5 . . . magnetization fixed layer

[0330]5 a . . . first magnetization fixed layer.

[0331]5 b . . . second magnetization fixed layer (reference layer)

[0332]5 c . . . non-magnetic conductive layer

[0333]6 . . . tunnel barrier layer

[0334]7 . . . magnetization free layer

[0335]9 . . . ferromagnetic tunnel junction

[0336]11 . . . memory cell

[0337]23, 24 . . . pad

[0338] WL, WL1, WL2 . . . word line

[0339] BL . . . bit line

1. In a magnetoresistive effect element having a pair of ferromagneticlayers opposed to each other through an intermediate layer to cause anelectric current to flow in the direction perpendicular to the layersurface to obtain a magnetoresistive change, said magnetoresistiveeffect element characterized in that at least one of said ferromagneticlayers includes an amorphous ferromagnetic material whosecrystallization temperature is higher than 623 K:
 2. A magnetoresistiveeffect element according to claim 1, wherein said magnetoresistiveeffect element is a spin-valve type magnetoresistive effect element inwhich one of said ferromagnetic layers is a magnetization fixed layerand the other is a magnetization free layer.
 3. A magnetoresistiveeffect element according to claim 1, wherein said magnetoresistiveeffect element is a tunnel magnetoresistive effect element using atunnel barrier layer made of an insulating material or a semiconductormaterial as said intermediate layer.
 4. A magnetoresistive effectelement according to claim 1, wherein magnetoresistive effect elementincludes a synthetic ferrimagnet structure.
 5. A magnetoresistive effectelement according to claim 1, wherein said amorphous ferromagneticmaterial is a ferromagnetic material mainly composed of any one of ormore than two kinds of Fe, Co, Ni, said ferromagnetic materialcontaining more than one kind of B, Si, C, P, Al, Ge, Ti, Nb, Ta, Zr, Moas additive elements.
 6. A magnetic memory device comprising: amagnetoresistive effect element having a pair of ferromagnetic layersopposed to each other through an intermediate layer to cause an electriccurrent to flow in the direction perpendicular to the layer surface toobtain a magnetoresistive change; and a word line and a bit linesandwiching said magnetoresistive effect element in the thicknessdirection, wherein one of said pair of ferromagnetic layers contains anamorphous ferromagnetic material whose crystallization temperature ishigher than 623 K.
 7. A magnetic memory device according to claim 6,wherein said magnetoresistive effect element is a spin-valve typemagnetoresistive effect element in which one of said pair offerromagnetic layers is a magnetization fixed layer and the other is amagnetization free layer.
 8. A magnetic memory device according to claim6, wherein said magnetoresistive effect element is a tunnelmagnetoresistive effect element using a tunnel barrier layer made of aninsulating material or a semiconductor material as said intermediatelayer.
 9. A magnetic memory device according to claim 6, wherein saidmagnetoresistive effect element includes a synthetic ferrimagnetstructure.
 10. A magnetic memory device according to claim 6, whereinsaid amorphous ferromagnetic material is a ferromagnetic material mainlycomposed of any one of or more than two kinds of Fe, Co, Ni, saidferromagnetic material containing more than one kind of B, Si, C, P, Al,Ge, Ti, Nb, Ta, Zr, Mo as additive elements.